Sky at a Glance | October 4th, 2013

Watch the Moon pass above Venus and Antares these evenings. (These scenes are drawn for the middle of North America. European observers: move each Moon symbol a quarter of the way toward the one for the previous date. For clarity, the Moon is shown three times actual size.)

As the stars begin to come out in twilight, Cassiopeia is already higher now in the northeast than the sinking Big Dipper is in the northwest. Cassiopeia's broad W pattern tilts up during the evening to stand on end.

New Moon (exact at 8:35 p.m. EDT).

Saturday, October 5

If you stay up past midnight this weekend, look east-northeast to catch bright Jupiter on the rise. Castor and Pollux are to its left. Much farther to its right, wintry Orion is coming up too.

Sunday, October 6

Jupiter is at western quadrature this week, 90° west of the Sun in the morning sky. This is when, in a telescope, the western edge of Jupiter is most clearly dimmer than its eastern, more sunward-facing edge.

Monday, October 7

During twilight, the waxing crescent Moon shines to the right of Venus. Well to the Moon's lower right, while twilight is still fairly bright, binoculars show Saturn above Mercury.

Tuesday, October 8

The Moon shines above Venus in twilight. Depending on where you are in North America, the Moon, Venus, and fainter Antares form a nearly equilateral triangle, as shown at right.

Wednesday, October 9

Look for Venus far lower right of the Moon during and after twilight. Just 3/4° above Venus is 2nd-magnitude Delta Scorpii.

Thursday, October 10

Do you know the landmark binocular double stars of western Capricornus? Everybody should, say I; you'll never forget them. This is the season. See Gary Seronik's Binocular Highlight column and chart in the October Sky & Telescope, page 45.

Triple shadow transit on Jupiter. A rare case of three moons — Io, Europa, and Callisto — casting their tiny black shadows onto Jupiter at the same time happens late tonight, from 4:32 to 5:37 Universal Time October 12th (12:32 to 1:37 a.m. Saturday morning Eastern Daylight Time). Jupiter will be high and best placed for telescope users in Europe and Africa, and low in the east for eastern North America.

Saturday, October 12

Venus has been approaching dimmer orange Antares, which twinkles to its left. They're now 4½° apart in the southwestern twilight. They'll pass 1½° from each other on October 16th.

Want to become a better amateur astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope.

This is an outdoor nature hobby. For an easy-to-use constellation guide covering the whole evening sky, use the big monthly map in the center of each issue of Sky & Telescope, the essential guide to astronomy. Or download our free Getting Started in Astronomy booklet (which only has bimonthly maps).

The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6  which may sound like a lot, but that's less than one star in an entire telescopic field of view, on average. By comparison, Sky Atlas 2000.0 plots 81,312 stars to magnitude 8.5, typically one or two stars per telescopic field. Both atlases include many hundreds of deep-sky targets  galaxies, star clusters, and nebulae  to hunt among the stars.

Can a computerized telescope replace charts? Not for beginners, I don't think, and not on mounts and tripods that are less than top-quality mechanically (able to point with better than 0.2° repeatability, which means heavy and expensive). As Terence Dickinson and Alan Dyer say in their invaluable Backyard Astronomer's Guide, "A full appreciation of the universe cannot come without developing the skills to find things in the sky and understanding how the sky works. This knowledge comes only by spending time under the stars with star maps in hand."

This Week's Planet Roundup

Oval BA. It shows up on all of my videos this morning."" credits="S&T: Sean Walker" width="" height="" align="right"]Mercury (magnitude –0.1) remains deep in the glow of sunset. About 30 minutes after sunset, use binoculars to look for it 20° lower right of Venus. Saturn (magnitude +0.7) glows 6° above Mercury early in the week, and a similar distance upper right of it by week's end.

Mars (magnitude 1.6, in Leo) rises around 3 a.m. It glows in the east in early dawn with Regulus below it. Compare their colors! The gap between them shrinks from 6° on the morning of October 5th to 2° on the morning of the 12th. They'll pass a bit less than 1° apart on the morning of the 15th.

In a telescope, Mars is still just a tiny blob 4.5 arcseconds wide.

Jupiter (magnitude –2.2, in Gemini) rises in the east-northeast around midnight. It blazes high in the southeast by early dawn. About 8° left of it are Castor and Pollux.

All descriptions that relate to your horizon — including the words up, down, right, and left — are written for the world's mid-northern latitudes. Descriptions that also depend on longitude (mainly Moon positions) are for North America. Eastern Daylight Time (EDT) equals Universal Time (also known as UT, UTC, or GMT) minus 4 hours.

Like This Week's Sky at a Glance? Watch our SkyWeek TV short, also playing on PBS.